Improve proc_open() configuration

[mikehaertl]

Issue mikehaertl/phpwkhtmltopdf#78 describes a problem that could be fixed with a different pipe configuration, as found here:

http://php.net/manual/en/function.proc-open.php#97012.

I've adopted this in release 1.0.5:

1 => array('pipe', 'w'), // stdout
2 => array('pipe', 'a') // stderr

But this caused new problems as now error capturing seemed to be broken as reported in issue mikehaertl/phpwkhtmltopdf#111.

So the change was undone in 1.0.6:

1 => array('pipe', 'w'), // stdout
2 => array('pipe', 'w') // stderr

A workaround would be, to use one or the other, depending on the OS. But so far I have no information from mikehaertl/phpwkhtmltopdf#78 which OS is really affected. Windows was only my (unconfirmed) assumption.

[epicwally]

Responding to your comment on #9: It does seem to work with adding the stream_set_blocking() while leaving the pipe configuration the same.

[markdboyd]

@mikehaertl - I ran into the same issue as #20. And I can also confirm that adding the stream_set_blocking() lines while leaving the pipe configuration the same fixes it.

I'm on version 2.2.1 of mikehaertl/phpwkhtmltopdf, if that helps.

[mikehaertl]

@markdboyd I'm worried that changing things in the proc_open() code breaks other stuff again. It's so touchy. This happened before and I had to undo the changes. (See #20 and #21).

So before we don't have proper test cases to reproduce all these problems I'm still hesitant to change the code. I'd be more than happy if someone could help out here. We can continue discussion in #20.